Mixing circuit for television cameras



June 6, 1950 s. R. PATREMIO MIXING CIRCUIT FOR TELEVISION CAMERAS 2 Sheets-Sheet 1 Fifea Feb. 9, 194s S. R. PATREMIO MIXING CIRCUIT FOR TELEVISION CAMERAS June 6, 19.50

2 Sheets-Sheet 2 Filed Feb. 9, 1946 Mw W. ma INVENTOR BY Maf/Maw Patented June 6, 1950 UNITED STATES PATENT OFF-ICE.

I 2,510,714 imXING CIRCUIT FonJ T'I'gEv'sioN CAMERAS Salvatore Robert Patremid Rochelle Park5 assigner to Allen B. Du Mont Laboratories, Incl., Passaic, N. J., a corporation of Delaware Application February 9, 1948, Serial No. 546,626

(o1. iis- 7.1)

1 Claim.

This invention relates to -meansfor changing from one television camera to another in such a way that a video signal can be obtained from either camera, or a mixed video signal can be obtained from both. Y Y

In carrying out the invention provision is made to cause the video signal from one of the cameras to fade out gradually while the video signal from the other one comes on gradually. In this Way pictures on receiving sets can be received from either camera, and when the video signal from it is being 'ad'ed out the video Signal from the other one is gradually Corning on so that the signals are blended during' Vthe change over time. During the change overl tiine the video signal `that is being transmitted gradually fades while the signal from the oncoming camera gradually increases until it is the entire video signal.

The invention may be understood from the description in connection with the laccompanying drawings in lwhich Figs. 1a and 1bv show a diagram of connections showing how the invention can becarried out. Y

In the drawing, reference characters I and 2 indicate the coaxial inputs of two camera signals that may be used separately or in such away that the video signals therefrom are blended or made to fade in and out with .respect to each other. The indicating lights for the cameras are shown at 3 yand 4 respectively. These lights glow when cameras are used. They indicate the camera or cameras that are in use on the output line.

An amplifier 5 is provided for the output of camera I and an amplifier 8 is provided for the output of camera 2.

The electromagnetic relay 1 is provided for operating the switches 8 and 9,l electromagnetic relay I8 for operating the switches II, I2 and I3, and the electromagneticrelay I4 for operating the switches I5, I8, I1 and I8. These electromagnetically operated switches are biased to their upper positions when their respective electrornagne'tic relays are not energized.

The 'push button I9 is providedvlfor operating the switches 28 and 2|. Contact 28 is provided for switch 28. TheipushbuttonZZ is for operating the switches 23 and 24 and the push button 25 is for operating the switches '28 and 21. Leads 2g and 21 are provided for the switches 25l and 21; Y

rI he output of camera I is coupled by lead 38 and parallel condensers 3I and 32 to contact 35 of switch II and to switch I6. 34 extend from this lead 38 to ground on opposite sides of these condensers.

Resistors 3: and' The output of camera 2 is coupled by lead 36 and parallel condensers 31 and 3 8 to contact 4I of switch I2 and resistors 39 and 48 are connected from lead 38 to ground on opposite sides of these condensers 31 and 38; vThe switch arm I2 is connected by lead 41, variable potentiometer 48 and condenser 48 to the control grid of the tube Si. Lead tiilconnects, switch I2 to the'switch I1. Lead 5I connects lead 38 to the contact 52 of switch I1. y l

Leads 55 and 56 are from a source of power, which may bellOvolts. Lead`55 extends to con- -tact .51 of switch 24 and lead 55 extends to solenoid I4. Lead 58 connects the other end of the solenoid I4 to contact 59 of switch ivan'd lead 58 vfrom contact 59 extends to the switch 21.

Lead 8l extends from the line 55 of the power line to switch 28 and contact 28 of this switch is connected by lead 82to switch 23. Lead 6-3 extends from the line 55 of the power line to the contact 64 of switch 2i, and lead 65 extends from lead 63 to the contact 66 Vof switch I3.

Lead 81 extends from switch ZI to one end of solenoid 1, the other end of this solenoid being connected by lead 58 to a lead 69 which extends Afrom power `line `55 to contact 18 to switch 9.

Lead 1I extends from lead 61 to the switch arm I3. Lead 15-extends from the switch 9 to the lead 13 which connects to the switch 24. Lead 14 extends `from contact 15 of switch 22 to the switch I8. Lead 15 extends from lead 13 to the lower end vof solenoid I8, the other end of this solenoid being connected by lead 11 to the power line 56. Y

The indicating lights3 and 4,are connected to one side of a source o f low voltage and to contacts 'I8 and 19 of switch 8 respectively. Contact 18 is connected by lead 83 to the switch I5 and contact 19 is connected by lead 8| to the contact 82 of switch I5.

The resistors 85 and 86 are grid leaks for the tubes 5 and 5 respectively and the cathodes oi.' these tubes are biased Vby resistors '81 and 88 respectively. The plates of tubes and 6 are conotd to a source of power through load resistor 88a,v decoupling resistor 881) and inductance 89. A 'point between resistors 88a and 886 is coupled bycapacitor 98 to ground. The connection from the source of power for tubes 5 and 6 tothe plates ofvthese tubes is 'shown at 9I and 92. The screen grids of these tubes are connected together by leads Stand and to a power source through resistor 93a and through capacitor 93 to ground. The suppressor grids of these tubes are connected in the usual way. A variable inductance coil 96 is located in the output of the tubes 5 and 6.

When the parts are in the positions shown in full lines in the drawing the camera I is ready for transmitting the video signal. The signal is carried from camera I by lead 3D, contact 35, switch I I, lead 42, resistor 43 and condenser 44 to the control grid of amplifier 5. The output lead 9| is connected to coil 96 in the video output lead 91 and the signal may be further` amplified in the usual Way. It may also be fed to a monitor, not shown, when desired.

During this time line current flows from lead 55, through lead 69, lead 68, solenoid 1, lead 61, lead 1I, switch I3, contact 66, lead 65, lead 63 to lead 56. 'I'his activates solenoid 1, pulling switch 8 down on contact 19. The indicating light 4 for camera I is lighted by current through it from one terminal of the source of current and through contact 19 and switch 8 to the other terminal of the source of current to show that camera I is operating.

When it is desired to transmit from camera 2 the button 22 is pushed down whereupon the switch 23 is opened and the switch 24 is closed.

The circuit is thus closed from power line 55 through contact 51, switch 24, lead 13, lead 16, solenoid I8, lead 11, to power line 56. This energizes solenoid I8, thus opening switches Il and I3 and closing switch I2. The closing of switch I2 establishes a video circuit from camera 2 through lead 36, contact 4I, switch arm I2, lead 41, resistor 48 and condenser 49 to the control grid of amplifier 6. The output lead is connected to the coil 96 as described in connection with lead 9|. This opening of switch II opens the circuit of the Video output from camera I. The opening of switch I3 opens the circuit of solenoid 1. This permits the bias spring of switch 8 to pull the arm'8 back up to the Contact 18, putting indicator light 3 in the circuit to show that camera 2 is operating.

When it is intended for the camera I to be connected again, the push button switch I9 is pushed downward thus opening switch 26 and closing switch 2 I. This establishes a circuit from power line 56 through lead 63, contact 64, switch 2|, lead 61, solenoid 1, leads 68 and 69 to power line 55. This energizes solenoid 1, thus opening switch 9 and causing current from power line 55, 56 to be cut on' from solenoid I0, whereupon spring biased switches II and I3 close and switch I2 opens. This closing of switch II establishes a video circuit from camera I through lead 38, contact 35, switch II, lead 42, resistor 43 and condenser 44 to the control grid of amplier 5. The output lead is connected to coil 96 as described in -connection with lead 9|. This opening of switch I2- opens the circuit of the video output from camera 2.

Closing the circuit through solenoid 1 also causes the spring biased switch 8 to close on contact 19 thus again lighting the indicating light 4 of camera I.

When it is desired to cause the signals of the cameras to overlap or to cause one to dissolve into the other the button is pushed down. This establishes a circuit from power line 55 through lead 6I, switch 20, lead 62, switch 23, contact 15, lead 14, contact 21', switch 21, lead 60, lead 58 and solenoid I4 to power line 56. This energization of solenoid I4 closes switches I5, I6, I1 and I8. This closing of switch I5 energizes both of the indicating lights 4 and 3 of the cameras I and 2. The circuit through the indicating light 4 of camera I from the 6.3 volts is from one side of the 60 cycle 6.3 volt source through switch 8, contact 18, lead 80, switch I5, contact 82, lead 8|, through indicating light 4 t0 the other side of the 6.3 Volts. The circuit through the indicating light 3 of camera2 is completed through switch 8 and contact 18.

When the solenoid I4 is energized by pushing the button 25 as described above and with the switches I6 and I1 thereby closed by this solenoid, connections are established: from camera I to inductance 96 by lead 38, switch I6, contact 46, lead 45, lead 42, resistance 43 to the control grid of tube 5 and from plate of this tube by lead 9I to inductance 96: and from camera 2 to this same inductance by lead 36, lead 5I, contact 52, switch I1, lead 50 and lead 41 to control grid of tube 6 and from the plate of this tube by lead 92 to inductance 96, thus mixing the signals from cameras I and`2.

Resistances 43 and 48 control the amount of video information from camera I and camera 2 respectively.

What is claimed is:

In a television signal switching device having two sources of television signal voltage, two amplifiers having separate input circuits and a common output circuit, and a pair of switches each of said switches being connected between a respective one of said sources and the input circuit of one of said amplifiers to connect said signals to the respective input circuits, said switches being interlockedto render one of said switches inoperative when the other of said switches is operated, separate means to connect -both of said signal sources to the respective ampliiiers at the same time, said means comprising a third switch having two pairs of contacts, said pairs of contacts being connected in parallel respectively with said pair of switches, an interlocking connection between said third switch and Said pair of switches to allow only one of said switches to operate at a given time, and separate fader circuits for each of said ampliers, said fader circuits being connected between the respective signal sources and the input circuits of said amplifiers to control the signal voltages applied thereto.

SALVATORE ROBERT PATREMIO.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,017,883 Zworykin Oct. 22, 1935 2,043,997 Goldsmith June 16, 1936 2,142,339 Weaver Jan. 3, 1939 2,146,512 Phinney Feb. 7, 1939 2,164,297 Bedford June 27, 1939 v 2,193,869 Goldsmith Mar. 19, 1940 2,286,540 Hanson June 16, 1942 OTHER REFERENCES Proceedings I. R. E., vol. 29, pages 250 to 265, 1941.

Television by RCA Institute Press, vol. II, Oct. 1937, pages 181 to 187.

Proceedings I. R. E., vol. 29, No. 6, June 1941, pages 303 to 309. 

